Made a makefile show its progress consistently, by listing only the source file names.

That change avoids the confusion of seeing some names shown twice.
Added basic frame for new target 'creativision'.

Kym Greenshields <kym.greenshields@gmail.com> has expressed interest
in contributing and maintaining support for the VTech CreatiVision system.
Fixed ca65's "ubiquitous_idents" feature.

Before the fix, that feature couldn't recognize a standard op-code mnemonic, that wasn't replaced by a macro, if it was on a line without a label.

This patch was written by Jeremy Turner.
Removed a now-redundant line.
Added a top border to a file's header comment.
Merged branch "master" into ubiquitous.
Merged branch "master" into make.
Merge pull request #62 from greg-king5/ubiquitous

Ubiquitous
Merge pull request #61 from greg-king5/make

Consistent makefile progress report
Revert "Added basic frame for new target 'creativision'."

This reverts commit 8e6b8dd0afed52c1963ea29c4921157693463cbe.
add SER_ERR_NOT_OPEN status code
add SER_BAUD_56_875
add serial driver for Atari, still contains much debug code
remove debug code
remove old (static) serial driver boilerplate
small optimzation (found by Greg King)
Merge pull request #64 from groessler/something_to_pull

Serial driver for Atari
Have %I yield values [1..12] instead of [0..11].
- Add a way to give additional compiler flags with USER_CFLAGS.
- Add possibility to specify an file name extension for generated executables (PROGEXT).
Merge pull request #66 from groessler/something_to_pull

New src/Makefile variables: USER_CFLAGS and PROGEXT